how are you going to prepare the follwoing phosphate solution which is used in many cell culture medium? 12 liters ;PH 7.4; 0.9%WT (total salts weight is 9.00 grams in one liter)
How many grams of what acid?
how many grams of the conjugate base?
You have two equations.
pH = pK2for H3PO4 + log (base)/(acid)
7.4 = pK2 + log b/a
solve for b/a and that's one equation.
The second one is
acid + base = molarity of solution.
Since you want 9g/L and that x 12L you want that many grams in the 12L. Convert that to M.
Then solve the two equation simultaneously for acid and for base; finally convert those to grams.